This invention relates in general to methods and compositions for protecting metal surfaces exposed to oxidative environments. The invention relates more particularly to methods and compositions for forming protective coatings on metal surfaces to inhibit the corrosive effects of oxidative environments thereon.
A common problem encountered in processes associated with oxidative environments such as processes for producing or enhancing the production of oil and/or gas from subterranean formations is corrosion of the metal surfaces of tubular goods and equipment used in the processes. The expense of repairing or replacing tubular goods and equipment damaged due to corrosion is extremely high.
Corrosion of metal surfaces is caused by a variety of oxidative environments. For example, in acidizing and fracturing treatments carried out to increase the permeability of subterranean formations, aqueous solutions containing acids and other corrosive compounds are typically introduced into the subterranean formations under pressure. The acid and other corrosive compounds can corrode metal surfaces of conduits, mixing tanks, pumps, casing and the like when contacted therewith. After the treatment is complete, the involved metal surfaces are still subject to attack by corrosive solutions and compounds such as brine, carbon dioxide and hydrogen sulfide remaining with spent treatment fluids, present in fluids that are produced from the formation and so forth. Damage to metal surfaces is exacerbated in oxidative environments associated with hostile conditions such as elevated temperatures.
Various methods and compositions have been proposed to solve or decrease the problems to metal surfaces caused by oxidative environments. Most methods and compositions developed heretofore, however, are not effective at temperatures above about 300 F. and/or do not form a protective coating that provides residual protection for an extended period of time.